Chap. I. 



THE MUSCLES. 



271 



place in this family in proportion as the ossification of the skin advances. This 

 is the muscle above the ribs. 



The second muscle, the M. retrahcns capitis collique, is below the ribs. This 

 muscle is peculiar to the Turtles, the conditions of its existence being a solid 

 trunk and a very movable neck. It originates from the bodies of all or most 

 vertebrae of the trunk, and is attached to the articulating processes of the vertebrae 

 of the neck and to the occiput. In some Turtles, it would be better to consider 

 it as divided into two distinct muscles,^ as its action is not always simultaneous. 



' Bojanus has described these muscles as one, 

 in accordance witli thi; subject of his investigations, 

 the Emys europasa, in which llic division into two 

 muscles is much less marked than in many otlicr 

 genera, Ozotheca, for instance. In Eniys serrata, we 

 find it as in Emys europa\a. In Emys C(mccntrica, 

 the muscle is one, originating from the eighth to the 

 sixth dorsal vertebra, and attached from the sixth 

 to the fourth neck vertebra i and with a long tendon 

 to the occiput. In Emj-s geographica and Lesueurii, 

 it is the same. In Cistudo virginea, it arises from 

 between the ribs near the tenth to tlie second dorsal 

 vertebra to the seventh and fifth neck vertebra- and 

 the occiput. In Ozotheea odorata, we see distinctly 

 two muscles. One of them, the M. retrahens colli in- 

 ferioris, originates on each side of the dorsal column 

 from tlie base of the third to the tifth rib, and is 

 attached laterally to the penultimate (eighth) vertebra 

 of the neck. This muscle draws the lowest part of 

 the neck backwards and upwards. The other, the M. 

 retrahens capitis collirpie superioris, originating from 

 the bases of the fifth to the seventh ribs, is attached 

 with one tendon to the uppermost part of the sixth 

 neck vertebra, willi anutlicr to the occiput. This 

 muscle draws tiie uppermost part of the neck and the 

 head backwards. When Ozotheea retracts its large 

 head, which it does faster than any other Turtle, 

 botli muscles first operate simultaneously, but soon 

 the short M. retrahens colli inferioris is entirely 

 contracted, while the other is drawing further. 

 Beyond these two muscles, we find in this genus a 

 third muscle much developed, which serves the same 

 purpose. Tlie M. latendis retrahens ultimo; verte- 

 bra; colli, originating from the base of the second 

 rib and the space between this and the third, and 



atlaehed to the uppermost lateral part of the last 

 (ninth) neck vertebra. This muscle is strong also 

 in Cistudo virginea, where, however, it originates 

 only from the base of the second rib. In our Green 

 Turtle, (Ciiclonia Mydas,) we find a distinct though 

 weak M. retraliens colli inferioris from the first dorsal 

 to the last neck vertebra, while the M. retrahens 

 capitis collique superioris is entirely wanting. But 

 at the same time, it is well known, that in this family 

 the power of retracting the head and tlie extremities 

 under the shield is very much reduced, indeed, almost 

 entirely wanting. On the contrary, in Testudo 

 tabulata these muscles are very strong. The if. 

 retrahens capitis collique superioris originates from 

 the seventh dorsal to the first sacral vertebra, and is 

 attached from the third to the fifth neck vertebra and 

 the occiput ; the M. retraliens colli inferioris, from 

 the first to the sixth dorsal vertebra, and from the 

 sixth to the ninth neck vertebra. Thus, both these 

 muscles occupy the dorsal column from the head to the 

 sacrum. In these land Turtles we observe, indeed, 

 the other extreme of what we have noticed in the sea 

 Turtles, as in them all structural elements are em- 

 ployed for the purpose of covering all the soft parts 

 by a thick, large shield, under which they are 

 retracted. In Chelydra serpentina, we may consider 

 these muscles as one, originating from near the tenth 

 to the fourth dorsal vertebra, (rather from the bases 

 of the ribs in this region,) and attached to the eighth 

 and seventh neck vertebra", and with a long tendon 

 to tlie occiput. In this family, however, this muscle 

 is not developed in the same degree as tlie remaining 

 muscular system, and particularly that of the legs 

 and tail, which is truly extraordinary, and aids in 

 the peculiar darting motions of riie body. 



